Are you still interesed to maintain this repository - shall I contribute back some changes?

Hey @exogen thanks for this piece of software. I have made some significant changes and wanted to know if you would be interested if I'd contribute them back? I'm asking first , because the last commit is quite a while ago.

Changes are:
* converted the code to Typescript
* dropped support for all `fetch` implementations except `node-fetch` (we use only this one)
* removed custom `HarHttp` and `HarHttp` classes (obsolete)
* remove `x-har-request-id` header and instead create separate agents on each request (we don't want that the receiver is able to filter requests via this custom header)

Let me know if you are still interested to maintain this repository! I would be glad.